Embodiments are provided that relate generally to muffling systems, and more specifically to muffling systems and apparatus capable of inducing high pressure drops and desirable flow properties. As used herein, the term “fluid” includes gases and liquids.
In a gas turbine engine, air is pressurized in a compression module during operation. The air channeled through the compression module is mixed with fuel in a combustor and ignited, generating hot combustion gases which flow through turbine stages that extract energy therefrom for powering the fan and compressor rotors and generate engine thrust to propel an aircraft in flight or to power a load, such as an electrical generator.
Within at least some known gas turbine engines, a portion of high-pressure air, such as, for example, bleed air from a compressor, is extracted or bled from the compressor for various needs. These needs include, for example, compressor flow bleeding which is used in order to improve operability as well as to provide, turbine cooling, pressurize bearing sumps, purge air or provide aircraft environment control. The air is bled off from the compressor using bleed slots located over specific portions or stages of the compressor. The extracted bleed air is then supplied to various locations in the engine via one or more bleed ports.
The problem: In least some known gas turbine engines, during engine operation occurring in some off-design operating conditions, the compressor may pump more air than is required for needs to include the combustion process. In order to manage operability of the engine and combustion performance, a portion of the excess bleed air from the compressor is routed through bleed conduits and dumped into a by-pass flow stream. The pressure and temperature of the air stream bled from the compressor may be very high. For example, embodiments include those wherein the bleed air stream pressure is greater than 200 psi and the bleed air temperature is greater than about 1000 Deg F. A transient bleed valve system (TBV) system is sometimes used for bleeding and exhausting the air removed from the compressor. Certain conventional designs for ventilation systems that dump the bleed air into the by-pass flow stream use a “Pepper-Pot” design. Such known conventional designs share limitations in that the Mach number of the flow exhausted into the by-pass stream may be high and also that the noise generated may be excessive. Furthermore, conventional designs are limited in that they only work when part of systems having metallic flow path structures that can handle the hot compressor air that is being routed through the TBV system. Additionally, some conventional systems are limited in that all the pressure loads in are managed by relatively few components causing high aero-mechanical loads and a potential for lower fatigue lives for those components. A new approach is required to reduce the pressures and mach numbers of the bleed air entering the by-pass stream or other locations further reducing the noise generated.
The solution: Embodiments are provided for a system that facilitates the reduction of the exposure of the flow path structures to the hot, high pressure and high-mach number air bled from the compressor or other sources. Embodiments are provided that facilitate reduction of the pressure of the flow in the bleed system and facilitate muffling of the noise generated, reduce temperatures and improve other flow properties, while protecting the flow path structures from damage due to exposure to hot air without causing significant disruptions in the flow streams. Additional embodiments and alternatives provide a system and device that exhausts a high-pressure source to a low-pressure sink while managing noise and exit flow distribution. Additionally, a tunable system is provided that is adjustable by easily performing modifications, as desired, to a limited number of components thereby providing pressure and Mach number reductions and also reducing noise.